Communication cable

ABSTRACT

A communication cable, and the method and apparatus therefore, made up of twisted strands of laid component conductors, wherein the component conductors are laid at pitches varying stepwise throughout their lengths and/or the strands are twisted at pitches varying stepwise throughout their lengths, whereby the production speed and efficiency are drastically increased as compared to conventional communication cable production techniques.

United- States Patent 1191 Akachi s 1 Feb. 13, 1973 I [54] COMMUNICATION CABLE 3,140,577 7/1964 "Ash ..57/s9 3,169,360 21965 C all t 1.... ....57 34 AT [75] Inventor:' Hisateru Akachi, Tokyo, Japan I on e a l 731' Assignee: Oki. Densen Kabushiki Kaisha, FOREIGN PATENTS APPUCATIONS a g Japan 859,179 12/1952 Germany ..57/63 [22] may Oct 7 1970 959,896 6/1964 H Great Britain ..5f7l63 [211 App]. No.: 78,870 Primary Examiner-Wemer H, Schroeder Attorney-Kelr'nan' and Berman 30 Forei n A lication Priori Data .1 8 pp ty [57] ABSTRACT t. 27, 1969 J ..44 85933 021.27, 1969 12:2: 44785934 A cmmun=icafin cable and mama and 5 1 1 paratus therefore, made up of twisted strands of laid 52 1 11.s.c1. ..57/156, 57/34 AT, 57/63, compmlem muductors wherein the 57 7 57 ductors are laid at pitches varying stepwise thi'oughout 511" 1 11.c1. ..H0lb 13/04, HOlb 11/04 their lengths and/or the strands are twisted at pitches [5 81 Field of Search..;...57/ 34 R, 34'AT, 58.3, 58.36, varying stepwise throughout their lengths, whereby the 57 5333, 59, 50, 52, 3, 4,6 7, ,91 production speed and efficiency are drastically in- 1 94, 156 creased as compared to conventional communication 1 cable production techniques. [515] Refei'ences Cited fl 9' 1 UNITED sTATEs PATENTS I 36 Claims, 24 Drawing Figures 2,069,316 1/1959, Lilly ..57/34 Af1 1/1 "I 2' 2 s1 31 e l PATENTEDFEH 13 I975 SHEET 01 0F FIGA PRIOR ART F IG. 5

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INVENTOR 'PATENTEDFEB 13 I973 SHEET 10 0F 03 5 Nm Q8 Q5 NNF mm 8 NEE INVENTOR BY: Maw Mp W AGm/rs COMMUNICATION CABLE The present invention relates generally to improvements in communication cables and, more particularly, to methods and apparatus adapted for the manufacture .of improved communication cables.

It is a common practice in forming a communication cable to have the adjacent pairs or quads of component conductors laid at pitches different from one pair or quad to the other and to have each of the pairs or quads laid at a uniform pitch throughout the overall length of the cable, whereby an occurance of crosstalking is prevented. Among the recent-developments of industrial communication cables is a rightand left-stranded cable (generally known as an 8-2 cable), in which the laying direction of each of the individual pairs or quads of conductors is inverted at predetermined unit length. This type of communication cable is, however, still considered as one of the variants of the conventional communication cables because the adjacent pairs or quads forming such cable are laid at pitches different from 'one pair or quad to the other and because the in- -dividual pairs or quads are laid at uniform pitches throughout the entire length of the cable.

Another recent version of the communication cables is a cable in which the pairs or quads are stranded in alternately inverted directions at every pitch so that any of the pairs or quads can be drawn out of the cable assembly at any point thereof simply by peeling off the protective sheath covering the particular point. The adjacent pairs or quads forming the communication cable of this type are, when viewed in a macroscopic fashion, invariably laid at pitches different from one pair or quad to the other and as such the communication cable may be said to be constructed in a manner basically similar to the construction principle of the conventional communication cables.

The speed of stranding communication cables presently available ranges from about 200 r.p.m. to about 2,000 r.p.m., varying with the types of cable stranding machines that include a planetary stranding machine, a torpedo stranding machine, a double stranding machine and so forth. Research and development is still under way with a view to increasing the stranding speed and to making available simplified production schemes and large-sized wire feeding reels and strand winding-up reels, including the development of the rightand left-stranded cable stranding system which has recently been commercialized.

The conventional principle of communication cable production which has been invariably accepted by the industry to date now places a crucial limitation on the continued improvement in the techniques of manufacturing communication cables on a commercially advantageous basis, because of the intensifying demand for an extremelyincreased production efficiency, at low cost, of communication cables. It is, therefore, of

'keen interest to the industry to seek for a drastically The present invention has its technical concept in the following new ,discoveries:

a. The cable in its entirety need not be stranded at one and the same pitch throughout the overall length of the cable but may be stranded at stepwisely varying pitches as long as the desired electrical and mechanical properties can be maintained. It is, in this instance, preferable that the cable be stranded at a constant pitch in each of the steps;

bjThe adjacent pairs or quads of component con ductors that form the communication cable need not be laid at such pitches that vary from one pair or quad to the other throughout the entire length of the cable, notwithstanding the fact that the two pairs or quads should be laid at different regular pitches.

c. Each of the individual pairs or quads need not be laid at one and the same pitch throughout the overall length of the cable (except for those portions of a rightand left-stranded cable at which the direction of stranding is inverted from the right to the left or vice versa),

but may be laid at stepwisely varying pitches unless irregular stranding of the cable is thereby caused and if the desired electrical properties are maintained and the resultant cable is endowed with satisfactory flexibility.

0n the basis of these new discoveries which in themselves are apparently contrary to the long accepted fundamental principle of communication cable production, the present invention aims, as its important object, at providing improved communication. cables which can be manufactured at an extremely increased production rate and at a low cost but which is capable of offering satisfactory electrical and mechanical properties comparable to those attainable in the communication cables that are presently in common use. In order to accomplish this object the invention proposes to provide, as entirely new and novel, a communication cable with its pairs or quads laid at stepwisely varying pitches and a communication cable which is stranded at pitches stepwisely varying throughout the overall length of the cable. According to the invention, such two types of cable configurations may be adopted either separately or, if desired, in combination to form a communication cable which is not only made up of such pairs or quads that are laid at stepwisely varying pitches but stranded at pitches varying stepwisely throughout the whole length of the cable.

It is another important object of the present invention to provide methods which are adapted for-the manufacture of the communication cables according to the invention, which methods are easy and economical to be put into practice because the number of consecutive steps required for completing the methods is significantly reduced as compared with the conventional practices of manufacturing communication cables.

It is still another important object of the present invention to provide apparatus adapted to carry out the methods according to the invention, the apparatus being made up of a significantly reduced number of operational elements and parts and can be constructed compactly without major modifications to the existing cable stranding machines. The communication cable stranding machine proposed by this invention are easy and economical to manufacture and to operate and can be readily used in combination with the existing wire feeding and cable winding-up machines.

The objects, features and advantages of the communication cables according to the present invention and the method and apparatus for the manufacture of the cables will become more apparent from the following description taken in conjunction with the accompanying drawings in which like reference numerals and characters designate corresponding parts in all figures and in which:

FIG. 1 is a schematic view, partially cut away, showing an embodiment of the improved communication cable according to the present invention;

FIGS. 2 to 8 are diagramatic views of the typical examples of the conventional communication cable stranding machines of various types including the rotary cable winding-up type (FIG. 2), the planetary type (FIG. 3), the built-in wire feeding roll type (FIG. 4), the double stranding type (FIG. 5), the torpedo type (FIG. 6), the single stranded type (FIG. 7 and 8), and the double stranding type with a built-in cable windingup roll (FIG. 9);.

FIG. 10 is a diagramatic view of a preferred embodiment of the communication cable stranding apparatus according to the invention;

FIG. 11 is a side elevation of a practical example of the apparatus basically constructed as illustrated in FIG. 9;

FIG. 12 is a view similar to FIG. 9 but now shows anotherpreferred embodiment of the communication cable stranding apparatus according to the invention;

FIG. 13 is a side elevation of a practical example of the apparatus shown diagramatically in FIG. 1 1;

FIGS. 14, 15 and 16 are diagramatic views showing some modifications of the apparatus illustrated in FIG.

FIG. 17 is a diagramatic view showing a communication cable stranding apparatus in which the apparatus shown in FIG. 9 is used as a cable drawing-out machine;

FIG. 18 is also a diagramatic viewv showing a commu nication cable stranding apparatus in which the apparatus shown in FIG. 11 is used as a cable drawing-out machine;

FIG. 19 is a diagramatic view showing still another modification of the communication cable stranding apparatus according to the invention, the modification being made to the conventional stranding machine of FIG. 18;

FIG. 20 is a side elevation of a practical example of the apparatus schematically illustrated in FIG. 19;

FIG. 21 is a diagrammatic view showing a further modification of the apparatus illustrated in FIG. 19;

FIG. 22 is a side elevation of a practical example of the apparatus schematically illustrated in FIG. 21;

FIG. 23 is a fragmentary sectional view showing a still further modified form of the communication cable stranding apparatus implementing the present invention; and

FIG. 24 is a front end view of the apparatus illustrated in FIG. 23.

Now, before entering into detailed discussion of the present invention, it may be mentioned that the term strand used as noun is intended to refer to a pair or quad of component conductors which are twisted around each other. It may also be mentioned that the term laying is herein used to refer to the twisting of the component conductors into a strand (which may be a pair or quad) and that the term stranding" is intended to mean the twisting of a plurality of strands into a stranded or assembled cable.

Referring to FIG. 1, there is illustrated a preferred embodiment of the communication cable according to the present invention. As shown, the cable which is generally represented by reference numeral 1 comprises strands 2 each of which is made up of component conductors 2a and 2b laid around each other, the strands 2 thus being herein shown as pairs. Designated by reference numeral 3 is a protective sheath which covers the strands 2; the protective sheath 3 is herein illustrated as partially removed so as to clearly show the variation of the pitches of stranding of the cable 1. The hatching with thick lines illustrates the stepwise variation of the stranding pitches of the cable 1 between portions indicated by reference characters A and B. As illustrated, the-component conductors 2a and 2b are laid around each other so as to form a single strand 2 and the pitches at which the component conductors 2a and 2b are laid together decreases stepwisely from portion A to portion B. It will thus be understood that the cable illustrated in FIG. 1 is a third type of the communication cable according to the invention, in which not only the component conductors but the strands formed thereby are twisted at pitches which vary in predetermined unit lengths but the elementary pitches in each of the predetermined unit lengths are kept constant.

The configurations of the communication cables embodying the present invention will be described in more detail as the description proceeds.

In the conventional techniques for producing communication cables, it is a common practice to use a capstan or a set of capstans whereby the cable is stranded at one'and the same pitch throughout the overall length of the cable. This will means that, if such capstans are removed from the cable stranding machine, then thecable would be stranded at pitches varying in one way or another. A specially designed slipping device is also usually provided in the existing cable stranding machine whereby the feeding reels and the winding-up reels are rotated in strict synchronism with the capstans. Provision of such a costly and intricately constructed slipping device, therefore, results in an increased production cost and a limited stranding speed of communication cables.

A typical example of the cable stranding machines presently in common use is illustrated schematically in FIG. 2. The cable stranding machine as illustrated comprises a series of feeding reels 10a, 10b, 10c, 10d, 10a, l0fand 10g on which are wound a series of strands 1 la, 11b, 11c, 11d, lle, 11f and 11g, respectively, which have been supplied from the preceding conductor laying stages (not shown). The strands 11a to 11g are passed between a pair of guide rolls l2 and 12' which are positioned posterior to the last feeding reel 10g as illustrated and which are rotated at regulated speeds. Past the guide rolls l2 and 12 is mounted an apertured disc 13. The disc 13 is rotatable freely about its center and has formed circumferentially therein a series of apertures not identified) through which the individual strands 11a to llg are passed and separated from each other. The strands 11a to 113 are configured, when being passed through the apertured disc 13 and thereby separated from each other, in a circular form as a whole when viewed in section. A hollowed rotary cylinder 14 is mounted in alignment with the apertured disc 13 and is driven for rotation in the direction of the arrow r. A forming die is mounted on the rotary cylinder 14 and positioned in line with the center point of the apertured disc 13 as illustrated. The strands 11a to 113 which have passed through the apertures of the disc 13 are fed into the forming die 15 rotating with the rotary cylinder 14 and are thereby stranded into a singlecable 1 1 at a predetermined constant pitch. A set of cooperating capstans 16 and 16. which are driven for rotation at a common circumferential speed are accommodated in the rotary cylinder 14 and are rotated, in their entireties, with the rotary cylinder 14 in the direction of the arrow r as shown. The cable 16 which has been formed as it leaves the rotating die 15 is thereafter drawn by the thus arranged capstans 16 and 16'. The rotary cylinder 14 further has accommodated therein a grooved pulley .17, a traversing device 18 adapted to move the grooved pulley 17 reciprocally in the directions of the arrow t at a fixed speed, and a cable winding-up reel 19 which is rotated about an axis rectangular to the axis of rotation of the rotary cylinder 14. The cable 11 which has been passed from the capstans 16,and 16' is then guided by the grooved pulley 18 and is wound uniformly on the winding-up reel 19 as the traversing device 18 reciprocates in the directions of arrow t. Here, it may be noted that the forming die 15, capstans 16 and 16', grooved guide pulley 1'7, traversing device 18 andcable winding-up reel 19 are all rotated about an axis which is in line with the direction in which the cable 11 advances in the rotary cylinder 14.

The winding-up reel 19 is usually provided with a mechanism (not shown) which is adapted to regulate both the speed of rotation of the winding-up reel 19 and the tension in the cable 16 to be wound on reel 19 in accordance with the speed at which the cable 11 is drawn by the capstans 16 and '16. Examples of such speed and tension regulating mechanism, as frequently put on practical use, are a slip-coupling brake and a torque motor.

If, now, the capstans 16 and 16 and devices required to drive the capstans for rotation are removed from the cable stranding machine illustrated in FIG. 2 are to be removed and if the cable winding-up reel 19 is rotated at a speed constantly proportional to the speed of rotation of the rotary cylinder 14 without use of speed and tension regulating mechanism, then the cable windingup reel 19 will actas capstans and as a result the whole construction of the cable stranding machine will be significantly simplified to the advantage of the production cost and efficiency, In this instance, the pitch of stranding of the cable will be dictated by the ratio between the speed of. rotation of the rotary cylinder 14 and the speed of rotation of the cable winding-up reel 19. If, now, the outside diameter of the winding-up reel (namely, the diameter at which the cable is initially wound on the reel) is D,, the outside diameter of the roll of the cable finally wound on the winding-up reel 19 is D,, the pitch of the cable initially stranded is P,,

and the pitch of the cable finally stranded is P,, then the following relationship will hold:

P,=P,. (D,/ D,) Eq. I it therefore follows that the pitch of stranding of the cable, starting with P will be increased stepwisely in unit lengths in which the cable is wound to form a common layer on the winding-up reel, terminating with P If the initial pitch of stranding is 200mm and the diameters D and D, are 500mm and 800mm respectively, the pitch of stranding of the cable will be increased stepwisely to 320mm. Experiments conducted by the inventorhave revealed that such stepwise variation in the pitch of stranding of a cable is fully acceptable at least insofar as the cables of about 300mm outside diameter are to be used. It will be, in this instance, understood that the communication cables stranded in this manner can be considered to be made up of a series of conventional cables which are connected to each other in a number corresponding to the number of layers of the cable wound on the winding-up reel and each of which is stranded at a pitch uniform in each of its unit lengths but different from the pitch of stranding of in any other unit lengths of the cables. This is the very reason for which the communication cables stranded at stepwisely varying pitches are sufficientlycomparable in electrical properties to the communication cables which are stranded at uniform pitches as practiced so far.

According to one important aspect of the present invention, therefore, a drastically improved communication cable which is stranded at stepwisely varying pitches is provided, the cable being stranded in such a manner that a plurality of strands (pairs or strands) of component conductors are drawn to and simultaneouslyv wound on a winding-up reel whichhas a drum and flanges of predetermined diameters and which is rotated in the direction in which the cable to be wound advances and that the rotary cylinder imparting to the winding-up reel a rotation about an axis which is in line with the direction of advancement of the cable is rotated at a speed related to the speed of rotation of the winding-up reel.

This type of communication cable according to the present invention may be produced with use of cable stranding apparatus of different constructions. An example of such apparatus is a cable stranding machine of planetary type, in which a series of feeding reels are mounted on a rotary cylinder and are rotated about an axis which is parallel to the direction of advancement of the strands of component conductors and a capstan and, a winding-up reel are rotated solely in the direction of advancement of the group of the individual strands. For application of the stranding machine of this type for the manufacture of the communication cable according to the invention, the capstan and a mechanism for regulating the rotation of the windingup reel are removed so that the winding-up reel is rotated at a speed relative to the speed of rotation of the rotary cylinder and that the winding-up reel serves not only for winding up the stranded cable but for drawing the cable from the twisting stage, similarly to p requirement for the installation in a factory of the apparatus, and and a reduced production cost of the communication cables produced by the apparatus and in the method hereinbefore outlined.

According to another important aspect of the present invention, a communication cable which is made up of the strands of component conductors which are laid around each other at pitches stepwisely varying throughout the overall length of the cable which the strands constitute. This type of improved cable can be produced in a manner essentially similar to the production of the previously described types of the communication cables according to the invention, namely, to the communication cables which are stranded at stepwisely varying pitches, as will be discussed in more detail in connection with the drawings. This second type of the communication cable embodying the present invention offers the same features as those attained in the first type of the communication cable which also embodies the present invention. Here, suffice it to say that the variation of the pitch of laying of the strands of component conductors is dictated by Equation 1 which has previously been presented.

It may also be mentioned in this instance that, although the elementary pitch of laying of the component conductors can be varied in any desired manner from one unit length to another insofar as the same is kept constant in each of the unit lengths, all the strands of component conductors should be laid at pitches regularly varying from one terminal to the other so as to have any adjacent strands laid at pitches different from one strand to the other. This requirement is completely met with by the communication cables constructed as hereinbefore described.

Although the winding-up reel has been hereinbefore discussed as rotated at a speed constantly proportional to the speed of rotation of the rotary cylinder, the rotation of the winding-up reel is closely related to the rotation of the feeding reels in the absence of the capstans so that the feeding reels in lieu of the winding reel may be rotated at a speed constantly proportional to the speed of rotation of the rotary cylinder.

According to a third important aspect of the present invention, the specific constructions of the above described two types of communication cables embodying the invention may be combined in a single communication cable which is characterized in that the component conductors to form each of the strands are laid at stepwisely varying pitches and in that the strands formed in this manner are stranded at stepwisely varying pitches throughout the whole length of the cable. Such construction arrangement of the third type of communication cable according to the invention will greatly contribute to the improvement in the production of communication cables on a commercial basis.

In the manufacture of such combined type of communication cables according to the invention, it is preferable that the strands of component conductors which are laid at stepwisely increasing pitches be stranded into a cable at stepwisely decreasing pitches. This is advantageous for the purpose of preventing the strands of component conductors from being further twisted or untwisted when the strands are twisted into a cable or of further increasing the variation of the pitches at which the component conductors are laid into a strand. It is, therefore, further preferable in the formation of the third type of communication cables that the component conductors and the strands formed thereby be twisted in the same direction and that the strands of component conductors laid at stepwisely increasing pitches be stranded into a cable at stepwisely decreasing pitches, whereby not only the individual component conductors can be prevented from being objectionably twisted or untwisted as the strands of the component conductors are stranded into a cable but also the individual strands are stranded in a direction in which the pitches of stranding thereof decreases.

Various methods and apparatus, and modifications thereof, which are adapted to produce the improved communication cables according to the present invention will be herein described but, for the better understanding of the features and advantages of such methods and apparatus, it will be of convenience to review constructions and operations of typical examples of the cable stranding machine which are now in common use.

FIG. 3 illustrates the basic construction of an existing cable stranding machine of planetary type, in which the speed of stranding is usually limited to the range of about rpm. to about 200 rpm. because of the fact that the feeding reels are disposed substantially on the same plane and mounted for rotation of a common rotary structure.

As seen in FIG. 3, the cable stranding machine of planetary type is shown to include feeding reels 10a and 10b which are mounted for rotation in casings 20a and 20b, respectively. The feeding reels 10a and 10b have wound thereupon strands 11a and 11b, respectively, and are rotated in the casings 20a and 20b, respectively, in a direction in which the strands 1 1a and 11b are unwound and fed therefrom. The casings 20a and 20b, in turn, are mounted for rotation on a rotary structure 21 which is rotated by a suitable driving source (not shown). Thus, the feeding reels 10a and 10b are not only rotated within the casings 20a and 20b, respectively, but revolved together about an axis in which the strands 11a and 11b are unwound and drawn from the respective feeding reels 10a and 10b as the rotary structure 21 is rotated. An apertured disc 13 is connected for rotation with the rotary structure 21 and has formed circumferentially therein apertures (not identified) corresponding in number to the number of strands to be passed therethrough. The strands 11a and 11b fed from the individual feeding reels 10a and 10b, respectively, are thus passed through the apertures formed in the apertured disc 12 which rotates with the rotary structure 22 and are then fed into a die 15 which is held stationary relative to the rotary structure 21. As the individual strands 11a and 1 lb are passed through the die 15, they are twisted into a stranded cable 11 with the apertured disc 13 and the rotary structure 21 rotating relative to the stationary die 13. The cable 11 thus formed is then drawn by a capstan 16 at a regulated speed. Where it is desired that an untwisting operation of the strands 11a and 11b are to be effected, the casings 20a and 20b may be rotated in the direction reverse to the direction of rotation of the rotary structure 21 by one turn per rotation of the structure 21. Unless such untwisting operation of the individual strands is required, the casings 20a and 20b are rotated together with the rotary structure 21 and the strands 11a and 11b are twisted as they pass through the apertured disc 13 and the die 15, as discussed above. As is apparent from the illustration of FIG. 3, the cable stranding machine of this type has drawbacks in that the cable stranding speed is critically limited because of the increased diameter of rotation of the individual casings 20a and 20b and because the feeding reels a and 10b are rotated relative to the respective casings 20a and 20b in directions rectangular to the direction'of advancement of the strands 11a and 11b which are unwound from the respective feeding reels 10a and 10b.

FIGS. 4, 5, 6, 7, 8 and 9 are presented to di'agramatically illustrate the relative sizes of the rotary structures and the basic principles of twisting the strands or component conductors in various types of conventional cable stranding machines using feeding reels of identical dimensions, wherein like reference numerals designate corresponding parts and elements and the dash-and-dot lines indicate the directions of advancement of the strands or the stranded cable.

Referring to FIG. 4 which shows an existing double stranding machine, two feeding reels 10a and 10b are juxtaposed in parallel to each other and are mounted for rotation about a common axis in a rotary structure 21. The rotary structure 21 can be rendered more compact and smaller-sized than the counterpart of the cable stranding machine of planetary type, because the feeding reels 10a and 10b can be mounted on a single rotary shaft (not shown). Since, however, the axis of rotation of the feeding reels 10a and 10b is still rectangular to the directions of advancement of the respective strands 11a and 11b as'illustrated, it is practically impossible to have the rotary structure 21 built in so reduced a size as to be capable of rotating at a sufficiently increased speed. As a matter of fact, the speed of rotation of the rotary structure 21 available with the stranding machine of this type is limited to the range of about 800 r.p.m. to about 1000 r.p.m. Represented by referencenumeral is an additional die over which the stranded cable 1 1 is passed clear.

FIG. 5 illustrates a modified form of the double stranding machine which is similar in function to the stranding machine shown in FIG. 4, wherein two feeding reels 10a and 10b are positioned in series with each other lengthwise in a rotary structure 21 so that the diameter of the rotary structure 21 can be considerably reduced. The reduction in the radius of rotation of the rotary structure 21 in this manner is, however, offset by an increased longitudinal length of the rotary structure 21, thus placing an unavoidable limitation to the reduction of the rotary structure 21 in its entirety. On top of this, since the axes of rotation of the two feeding reels 10a and 10b are rectangular to the directions of advancement of the strands 11a and 11b unwound respectively therefrom, a limitation is also placed to the speed of rotation of the rotary structure 21.

Illustrated in FIG. 6 is a cable stranding machine of torpedo type, which is essentially similar in construction arrangement to the stranding machine of FIG. 5 in that feeding reels 10a and 10b are, as shown, positioned -to be in series with each other in the lengthwise direction of the rotary structure or torpedo 21 thereby to reduce the diameter of the cylindrical portion of the rotary structure 21. Such reduction in the diameter is, similarly to the rotary structure of FIG. 5, sacrificed by the increased longitudinal length of the rotary structure 21. Since, moreover, the axes of rotation of the feeding reels are rectangular to the directions in which the strands 11a and 11b unwound respectively therefrom are made to advance and since the strand 11a drawn from the feeding reel 10a, which is remoter from an apertured disc 13 than the other feeding reel 10b as illustrated, must be passed clear of the feeding reel 10b while being rotated with the rotary structure 21, it is still required that the rotary structure 21 be constructed with a considerably large outside diameter resulting in a large radius of rotation of the rotary structure. The speed of rotation of the rotary structure 21 is, as a consequence, limited to the order of 1000 r.p.m. where feeding reels of usual size are employed.

Turning to FIG. 7, here is illustrated a conventional cable stranding machine of the type in which the stranded cable is wound-up within a hollowed rotary structure. The rotary structure 21 of the stranding machine of this type has accommodated therein a capstan 16, a grooved guide pulley 17, a traversing device 18 and a winding-up reel 19, as illustrated. The rotary structure 21 has also provided therein a mechanism which is adapted to have the speeds of rotation of the capstan 16 and the winding-up reel 19 synchronized during operation. Moreover, the winding-up reel 19 is rotated in a direction rectangular to the direction in which the stranded cable 11 advances toward the winding-up reel 19 inside the rotary structure 21 which is rotating. Thus, it will be understood that the speed of stranding of the communication cable with use of the stranding machine of this type is still subject to a certain limitation because various parts and members must be mounted inside the rotary structure 21 to add to the overall size and weight thereof and because the winding-up reel 19 and the rotary structure 21 accommodating the reel 19 are rotated in different relative directions. The speed of rotation of the rotary structure 21 in this example of the cable stranding machines is about 500 r.p.m. to about 700 r.p.m. where usual component conductors are to be used. The capstan 16 may be positioned outside the rotary structure 21 so as to decrease the overall dimensions and weight of the rotary structure but such will not result in a significant increase in the stranding speed of the cable, as will be readily understood.

FIG. 8 illustrates a modification of the cable stranding machine of FIG. 7, in which a grooved guide pulley 17, a traversing device 18 and a winding-up reel 19, all of which are invariably accommodated within the rotary structure 21, are positioned in such a manner that the stranded cable 11 is wound on the winding-up reel 19 in the same direction as the direction of rotation of the rotary structure 21, namely, the winding-up reel 19 is rotated about an axis in line with the axis of rotation of the rotary structure 21. With this improvement made to the cable stranding machine of FIG. 7, the speed of rotation of the rotary structure 21 can be increased to the order of 1000 r.p.m. but, because the rotary structure 21 must accommodate therein the various spacetaking components such as the capstan 16, pulley 17,

traversing device 18 and winding-up reel 19, can not be further increased to full satisfaction.

FIG. 9 illustrates one of the presently most advanced communication cable stranding machines of double stranding type whereby a considerably increased cable stranding rate can be attained.

Drawbacks inherent in any of the conventional cable stranding machines are still encountered in this advanced type of double stranding machine in that the rotary structure 21 has invariably accommodated therein a set of capstans 16 and 16. a grooved guide pulley 17, a traversing device 18 and a cable winding-up reel 19 and in that the axis of rotation of the winding-up reel 19 is rectangular to the axis of rotation of the rotary structure 21. The cable stranding machine of this type is nevertheless advantageous because all the components and parts to be accommodated inside the rotary structure 21 are supported in such a manner as to be held at rest in the direction rectangular to the axis of rotation of the rotary structure 21 so that it is the rotary structure alone that is subject to rotation. The rotary structure 21 thus arranged can be rotated at an increased speed of about 1000 r.p.m. to about 1200 r.p.m. resulting in a stranding speed .of about 2000 to 2400 pitches per minute. The performance efficiency available in this type of stranding machine is also improved because of the very fact that the machine is of the double stranding type. In spite of such an increased stranding speed and improved performance efficiency, the cable stranding machine herein shown is not fully acceptable for the extremely increased longitudinal length of the rotary structure 21.

The drawbacks and disadvantages which are inherent in any of the conventional communication cable stranding techniques as heretofore been pointed out are completely eliminated in the methods and ap paratus therefor according to the present invention, owing to introduction of a drastically new and novel concept that the strands of component conductors and/or the conductor to form the strand need not be stranded or laid at a uniform pitch throughout the overall length of the cable. Such new concept of communication cable stranding makes it possible to have the feeding reels and the winding-up reel positioned in amore reasonable configuration that will contribute to increasing the cable stranding speed, reducing the number of components and parts of the stranding machines, simplifying the entire process of the cable stranding operation, improving the performance efficiency of communication cable production, and significantly reducing the cost and labor required for the Manufacture of communication cables which are fully comparable in eros stalking preventive ability to those communication cables which are manufactured in the systems presently in common use. As a matter of fact, according to the present invention, the feeding and/or winding-up reels are positioned so that the axes of rotation of the reels are in alignment with the direction of advancement of a stranded cable or a strand of component conductors. The costly and intricately constructed mechanism which has been required to synchronize the speeds of rotation of the capstan and the reels is dispensed with in the apparatus proposed by this invention. The rotary structure of the constructions hereinbefore described and shown as invariably used in the conventional communication cable stranding machines of various types is also removed from the cable stranding apparatus according to the invention. Due to these and other improvements incorporated in the methods and apparatus according to the present invention, the, speed of communication cable stranding speed can be greatly increased to about 3000 r.p.m. to about 5000 r.p.m. The methods and the apparatus therefor as proposed by this invention, furthermore, can be modified in various manners so as to meet various requirements of communication cables.

The basic concept of the methods and apparatus which are adapted for the manufacture of the communication cables according to the invention will be understood from observation of FIG. 10 which diagramatically illustrates a fundamental construction of a first embodiment of the communication cable stranding apparatus according to the invention. As illustrated, the cable stranding apparatus essentially comprises an apertured disc 30 having formed substantially circumferentially therein a plurality of apertures (not identified) through which a plurality of strands which are shown as two in number by reference numerals 2 and 2' for instance are separated from each other and disposed on a substantially circular configuration when viewed in section, a rotary flyer 31 positioned in alignment with the apertured disc 30, a forming die 32 mounted centrally of the flyer 31 through which die the component strands 2 and 2 disposed regularly by the apertured disc 30 are stranded into a cable 1 as the flyer 31 is rotated, and a winding-up reel 33 positioned past the flyer 31 and rotated relative to the flyer about an axis which is substantially in line with the axis of rotation of the fiyer whereby the stranded cable 1 is wound on the reel 33 for storage. The winding-up reel 33 is reciprocated in the direction of axis of rotation thereof so that the cable 1 is wound thereon forming a plurality of layers. If, therefore, the winding-up reel 33 is rotated at a constant speed, then the cable 1 will be wound on the reel 33 at a speed stepwisely increasing from one unit length to another in which the wound cable forms an individual layer with the result that the pitch of stranding of the cable varies stepwisely at intervals determined by the reciprocating movement of the reel 33. The pitch of the stranding of the cable is, as will be discussed in more detail as the description proceeds, also determined by the relationship among the speed at which the strands 2 and 2' are fed, the speed of rotation of the flyer 31 and the speed of rotation of the windingup reel.

It should be understood in this instance that, although the apparatus is described in the above discussion as used for stranding the strands of component conductors to form a stranded or assembled cable, the same apparatus can be used for the purpose of laying the component conductors into an individual strand which is to eventually form a component of the cable.

Also, the apparatus described in the above is constructed and operated as a combination stranding and winding-up apparatus with the reel 33 serving as a cable winding-up reel but, if desired, the same apparatus may be utilized, without any modification thereto, as a combination feeding and stranding apparatus in which the reel 33 is employed as a feeding reel having wound thereon a set of parallel strands (or component conductors) which are fed and stranded in a direction inverted from the direction in which the strands are fed where the apparatus is used as a combination stranding and winding-up apparatus, as will be later described in more detail.

Thus, in the methods and apparatus according to the present invention, the previously generally accepted taboos are upset completely by the introduction of a new concept that the cable, or the component conductors to be stranded into the cable, can be stranded at stepwisely varying pitches. This new concept provides the outstanding features of the present invention in that the feeding or winding-up reel can be used as a capstan, that the cable or strands of component conductors can be wound or fed along a line aligned with the axis of I rotation of the reel and that the feeding or winding-up reel can be rotated about an axis of rotation about .which the strands or the component strands are twisted into a cable or a strand respectively.

Such new concept and the features of the methods and apparatus will be more clearly understood from the following description taken with reference to FIG. 11 which illustrates in detail a practical example of the constructions of the stranding apparatus diagramatically shown in FIG. 10.

The stranding apparatus shown in FIG. 11 comprises a set of cooperating capstans 34 and 34. which are driven from a main driving means or motor 35 through V-sheaves 36 and 37 whereby the strands 2 and 2' of previously laid component conductors or wires 2a and 2b (FIG. 1) are fed. The V-sheave 36 is driven from the main driving means or motor 35 through a power transmission shaft 38. Past the capstans 34 and 34' is mounted an apertured disc member 30 which, as previously mentioned with reference to FIG. 10, has formed substantially circumferentially therein a plurality of apertures (not identified in the drawing) through which the strands 2 and 2', shown as only two in number for simplicity of illustration, are separated from each other and disposed in a substantially circular configuration when seen in section. The apertured disc member 30 is supported to be freely rotatable about its center point around which the apertures are disposed. The rotary flyer 31 which is schematically illustrated in FIG. is supported by a stationary pedestal 39 through a rotary shaft 40 which is secured to the flyer 31 and which is rotatably journalled into the pedestal 39, as illustrated in FIG. 11. The rotary shaft 40 of the flyer 31 is driven for rotation either by the main driving means or motor 35 through a series of V-sheavcs 41, 42, 43 and 44 or by a torque motor 45 through the V-sheave 44 and a V- sheave 46 drivenby the torque motor 45. The V-sheave 41 is first driven by the main driving means or motor 35 through a gear 47 mounted on a shaft 470 coupled with the maindriving means or motor 35 and a gear 48 meshing with the gear 47 and mounted on a shaft 48a. The V-sheaves 42 and 43 carrying the driving power from the associated V-sheave 41 are supported on a transmission shaft 49 which is free for rotation with the V-sheaves 42 and 43. The V-sheave 44 is supported on a portion 40a of the rotary shaft 40 extending from the bracket 39 and conveys the driving power from the V- sheave 36 to the rotary shaft 40, thereby driving the flyer 31 to rotate in either direction as the case may be. The V-sheave 45, which is coupled with the torque motor 46'through a shaft 460, is driven by the torque motor 45 through the shaft 46a and carries the driving power to the associated V-sheave 44 so as to drive the flyer 31. Thetorque motor 45 is made operative only when the flyer 31 is not driven from the main driving means or motor 35 as will be discussed in detail as the description proceeds. As indicated by phantom lines, beltings are passed on the mutually cooperating V- sheaves as customary.

The rotary shaft 40 is hollowed in its axial direction and has mounted on the leading end of its extended portion 40a a forming die 32 as previously noted in connection with FIG. 10. The strands 2 and 2 of component conductors (which may be laid either at a uniform pitch as conventional or at stepwisely varying pitches according to the invention) are stranded into an assembled cable 1 as the strands are passed through and twisted by the die 32, as will be discussed later.

The flyer 31 has mounted thereon a support or supports 31a extended therefrom in the direction opposite to the forming die 32, as illustrated. A series of grooved guide pulleys which are herein shown as three in number by reference numerals 50, 51 and 52 are mounted rotatably on each of the supports 31a, whereby the stranded cable 1, which has been passed through the bore (not numbered) in the hollowed rotary shaft 40 from the forming die 32, is guided on the grooved guide pulleys 50, 51 and 52 in this sequence as seen in the drawing.

A winding-up reel 33, previously mentioned in regard to FIG. 10, is provided, which is supported by a pedestal 53 through a main shaft 54. The main shaft 54 is integral with the shaft 48a mounting thereon the V- sheave 41, and the gear 48 and is journalled through the pedestal 53 to be rotatable therein. The winding-up reel 33 has a pair of flanges 33a and 33b which are mounted on its axial ends. The winding-up reel 33 is rigidly secured to the main shaft 54 by means of a mounting flange 55 which is fast on the main shaft 54 and a clamping bolt 56 fixed to the leading end of the main shaft 54, as illustrated. The axis of the main shaft 54, the axis of rotation or the center point of the flyer 31, and the direction of advancement of the stranded cable 1 through the bore in the hollowed rotary shaft 40 are all in alignment with each other, which is characteristic of the apparatus accordingto the invention.

The main driving means or motor 35 and the pedestal 54 supporting the winding-up reel 33 are mounted on a table 57 which is slidable back and forth on a base table 58. The sliding table 58 is driven for sliding or reciprocating movement on the base table 58 by means of an auxiliary driving means or motor 59 through a coupling 59a.

The stranding apparatus thus constructed and arranged can be operated in four basically different manners depending upon the applications on which the stranding machine is placed. Firstly, the capstans 34 and 34 and the torque motor 45 are made operative and the power train through the V-sheaves 41, 42 and 43 are disconnected from the V-sheave 44, whereby a stranded cable is wound on the winding-up reel 33. Secondly, the capstans 34 and 34 and the torque motor 45 are held at rest and instead the flyer 31 is driven from the main driving means or motor 35 through a power train established by the sheaves 41, 42, 43 and 44, whereby a stranded cable is wound on the winding-up reel 33. Thirdly, the reel 33 is utilized as a feeding reel on which a separably combined parallel strands of laid component conductors as indicated by reference numeral 1' in FIG. 11 are wound. In this instance, the separably combined parallel component strands 1 are unwound from the reel 33 and are fed in a direction reverse to the direction of advancement of the stranded cable as in the first and second applications of the stranding apparatus. The flyer 31 is driven for rotation from the torque motor 45 through the V- sheaves 46 and 44 and the strands l are drawn by the capstans 34 and 34 and stranded as they pass through a second forming die 32 which is positioned between the apertured disc member 30 and the capstan 34. The thus stranded cable which is now. indicated by reference numeral 1 is wound on a winding-up reel which is positioned desiredly posterior to the capstans 34 and 34. The fourth application is similar partly to the second application and partly to the third application, because the reel 33 is used as feeding reel with separably combined parallel strands wound thereon and because the flyer 31 is driven from the main driving means or motor 35 through the power train including the sheaves 41, 42, 43 and 44 with the capstans 34 and 34' and the torque motor 45 kept inoperative. Thus, it will be understood that the apparatus of FIG. 11 can be utilized as a combination stranding and winding-up apparatus as in the first and second applications and as a combination feeding and stranding apparatus as in the third and fourth application. The differences between the cables resulting from the first and third applications and between the cables resulting from the second and fourth applications will become apparent from the description to follow. In any of the applications or the methods herein proposed, the reel 33 which may be utilized either as a winding-up reel or as a feeding reel is securely mounted on and rotated with the main shaft 54 and the axis of the main shaft 54 is substantially in line with the stranded cable (in the first and second applications) or the separably combined parallel strands (in the third and fourth applications). This is the very reason for which the cable stranding speed can be increased remarkably in the methods and apparatus according to the present invention.

In the following discussion of the four applications of the apparatus shown in FIG. 11, the apparatus is described as used for stranding the strands of laid conductors into a cable but it is quite apparent that the same apparatus can be used for the purpose of laying component conductors into a strand which is to finally form part of the assembled communication cable- First Application The strands 2 and 2' of component conductors which have been laid at a'preceding stage are wrapped on the capstans 34 and 34' and are thereafter passed over to the forming die 32 through the apertured disc 30, as illustrated in "FIG. 11. The strands 2 and 2' are stranded together into a cable 1 when they pass through the die 32 which is rotated together with the apertured disc 30 and the flyer 31. The flyer 31 is driven for rotation from the torque motor 45 through the V-sheaves 44 and 46 with the power train through the V-sheaves 41, 42 and 43 keptdisconnected from the flyer 31. The stranded cable 1 is passed over to the winding-up reel 33 through the grooved guide pulleys 50, 51 and 52 which are rotatably mounted on the support 31a extending from the flyer body 31. The stranded cable 1 is wound on the winding-up reel 33 as the flyer 31 is rotated around the reel 33. In this instance, the flyer 31 is rotated around the reel 33. In this instance, the flyer 31 serves not only to let the cable 1 be wound on the winding-up reel 31 but to let the strands 2 and 2 be drawn from the capstans 34 and 34'. The strands 2 and 2' and the resultant cable 1 are maintained at a substantially constant tension through adjustment of the speed of rotation of the torque motor 45. The winding-up reel 33 is secured to the main shaft 54 and is driven for rotation at a predetermined speed from the main driving means or motor 35 through the gears 47 and 48 meshing with each other. The capstans 34 and 34' are driven at a speed constantly proportional to the speed at which the winding-up reel 33 is driven from the main driving means or motor 35, thereby determining the elementary stranding pitch in every unit length of the cable 1. There are, in this instance, two different manners of winding the stranded cable 1 on the winding-up reel 33. That is to say, the cable 1 may be wound on the reel either in a manner that the flyer 31 is rotated in the same direction as and at a speed higher than the winding-up reel 33 thereby to have the cable I wound on the reel 33 at a rate corresponding to the difference between the speeds of rotation of the flyer 31 and the winding-up reel 33 or in a manner that the flyer 31 is rotated in a direction opposite to and at a speed lower than the winding-up reel 33 whereby the cable 1 is wound on the reel 33 at a rate corresponding to the difference between the circumferential speed of the winding-up reel 33 and the linear feeding speed determined by the rotation of the capstans 34 and 34'.

Assuming, now, that the flyer 31 is removed from the apparatus shown in FIG. 1 and that the winding-up reel 31 alone is rotated with the capstans 34 and 34' held at rest, then the strands 2 and 2' will be stranded into a cable 1 at a pitch corresponding to the speed of rotation of the winding-up reel. The thus stranded cable 1 is, in this instance, not wound on the reel 33, as will be readily understood.

If, then, the flyer 31 is mounted on the illustrated apparatus and rotated at a speed equal to the speed of rotation of the winding-up reel 31 with the capstans 34 and 34 still held at rest, the cable 1, stranded at the forming die 32, would not be wound on the winding-up reel 33 invariably, because there occurs no relative rotation between the reel 33 and the flyer 31, as will also be readily understood.

Now, if either one of the flyer 31 and the winding-up reel 33 is rotated at a speed higher than the other, then the stranded cable 1 will be wound on the reel 33 at a rate determined by the difference between the speeds of rotation of the flyer 31 and the reel 33. It will be understood in this instance that the direction in which the stranded cable 1 is wound on the winding-up reel 33 depends upon whichever of the flyer 31 and the reel 33 is rotated at a speed higher than the other. The difference between the speeds of rotation of the flyer 31 andthe winding-up reel 33 should be in agreement with the speed at which the strands 2 and 2 of component conductors are fed through the capstans 34 and 34'.

Thus, in the first application of the communication cable stranding apparatus shown in FIG. 11, the cable is stranded and wound on the winding-up reel either in a manner that the flyer 31 and the winding-up reel 33 are rotated at speeds different from each other with the capstans 34 and 34 serving merely as a guiding means that is allowed to rotate freely or in a manner that the capstans 34 and 34' are rotated at a constant speed with the flyer 31 allowed to freely rotate and with the torque motor serving simplyto impart a certain tension to the strands 2 and 2' and the resultant cable which are being fed.

The apparatus shown in FIG. 1 1 in this particular application utilized as a combination stranding and winding-up apparatus in which the capstans 34 and 34' are operative and the flyer 31 is driven for rotation from the torque motor 45 with the reel 33 serving as a winding-up reel.

Second Application The flyer 31 is rotated at a speed proportional to the speed of rotation of the reel 33 serving as a winding-up reel in this application. For this purpose, the flyer 31 is driven for rotation from the main driving means or motor 35 through the gears 47 and 48 and the V- sheaves 41, 42, 43 and 44 with the capstans 34 and 34' and the torque motor 45 kept inoperative. In this instance, both the flyer 31 and the winding-up reel 33 are driven by a common driving source so that the flyer 31 is rotated at a speed constantly proportional to or synchronized with the speed of rotation of the windingup reel 33, as will be readily understood. The elementary pitch of stranding of the cable is in each of the unit lengths, therefore, determined by the relative rotation between the flyer 31 and the winding-up reel 33. Similarly to the first application, there are available two different manners of winding the stranded cable on the winding-up reel 33, one of which is to have the flyer 31 rotated at a higher speed than the winding-up reel 33 and the other of which is to have the winding-up reel 33 rotated at a higher speed than the flyer 31.

While, in the first application, the flyer 31 is rotated at a speed stepwisely increasing as the length of the cable wound a turn on the reel 33 increases because the strands 2 and 2' are fed at a fixed speed so that the overall diameter of the roll of the cable wound on the reel increases stepwisely from one layer to another, the speed at which the cable is wound on the winding-up reel 33 per turn of the flyer 31 increases as the overall diameter of the roll of the cable wound on reel 33 in this second application of the apparatus shown. It therefore follows that the elementary stranding pitch in every unit length of the resultant cable is determined by the speed of rotation of the reel 33 and the speed at which the strands 2 and 2 of component conductors are fed (so that the primary stranding pitch in each of the intervals of the cable is dictated by Equation 1) and that the stepwise variation of the pitches from one unit length to another is dictated by the variation in the speed of rotation of the flyer 31. v

The tension at which the stranded cable is wound on the winding-up reel 33 is determined through regulation of the operation of the torque motor in the first application, while the same is determined by the back tension applied to the strands 2 and 2' of component conductors in the secon application.

It may be mentioned in this instance that where, in the first application of the apparatus shown, the flyer 31 is rotated at a speed higher than the speed of rotation of the winding-up reel 33, the'torque motor 45 can be substituted for a braking device of suitable type. In this instance, the tension in the stranded cable to be wound on the reel 33 is determined by the braking effort exerted by the braking device.

Third Application The third application of the apparatus shown in FIG. 1 1 is different from the first and second applications in that the reel 33 is used not as a winding-up reel but as a feeding reel on which a desired number of readily separable parallel strands of laid component conductors are wound. The thus combined parallel strands are separated and stranded into a cable. Advantages of this application are that the number of the feeding reels to be used can be reduced significantly and that the cable stranded is free from one-sided listing.

The separably combined parallel strands 2" and 2" wound on the reel 33 which now acts as a feeding reel are unwound and guided by the grooved guide pulleys 52, 51 and 50 over to the die 32 through the bore in the rotary shaft 40, as indicated by dotted lines in FIG. 11. The strands 2" and 2" are then passed through the apertured disc 30 and are thereby separated from each other. An additional forming die 30' is mounted immediately before the capstans 34 and 34' so that the strands 2" and 2" separated by the apertured disc 30 are twisted as the flyer 31 and accordingly the apertured disc 30 are rotated. The thus stranded cable which is now represented by reference numeral 1' is fed to a winding-up reel (not shown) through the capstans 34 and 34. The parallel strands are unwound and fed from the reel 33 at a rate corresponding to the difference between the speeds at which the flyer 31 and the reel 33 are rotated, as in the first and secon applications. If, in this instance, the flyer 31 is to be rotated at a speed higher than the speed of rotation of the reel 33, then the flyer 31 should be driven for rotation by the torque motor 45 through the V-sheaves 46 and 44. If, conversely, the flyer 31 is rotated at a speed lower than the speed of rotation of the reel 33, then the flyer 31 should be driven for rotation by the torque motor 45 or a suitable braking device which is not shown. In this instance, the tensions in the parallel strands 2' and 2" are determined by the voltage applied to the torque motor 45 or by the braking effort exerted by the braking device. It may be mentioned that the parallel strands 2 and 2" are unwound and fed from the reel 33 at a fixed speed, and the pitch of stranding of the cable 1 is stepwisely varied with the variation in the speed of rotation of the flyer 31, as in the first and second applications previously discussed. It may also be mentioned that, although the strands wound on the reel 33 have been hereinbefore described as being separably combined in parallel to each other, a plurality of strands may be wound in parallel to each other and in the same length on the reel 33, if desired.

Fourth Application The fourth application of the apparatus shown in FIG. 11 is the combination of the second and third applications in that the flyer 31 is driven from the main driving means or motor 35 and that separably com- 

1. A method of manufacturing a twisted communication cable unit whose twisting pitch varies stepwise from one end of the unit to the other, which method comprises: a. continuously supplying a plurality of elongated strands of laid conductors at a predetermined rate; b. twisting said strands around each other and thereby forming an elongated cable unit; c. passing said cable unit longitudinally through an apertured member mounted for rotation about an axis extending substantially in the direction of elongation of said unit; d. winding said cable unit on a reel while rotating said reel substantially coaxially with said member and at a constant speed proportional to said rate; and e. rotating said member at a speed different from the rotary speed of said reel and varying stepwise, while said cable unit is being wound on said reel in successive layers, the variation in the rotary speed of said member being sufficient to impart to said cable unit a stepwise varying pitch.
 1. A method of manufacturing a twisted communication cable unit whose twisting pitch varies stepwise from one end of the unit to the other, which method comprises: a. continuously supplying a plurality of elongated strands of laid conductors at a predetermined rate; b. twisting said strands around each other and thereby forming an elongated cable unit; c. passing said cable unit longitudinally through an apertured member mounted for rotation about an axis extending substantially in the direction of elongation of said unit; d. winding said cable unit on a reel while rotating said reel substantially coaxially with said member and at a constant speed proportional to said rate; and e. rotating said member at a speed different from the rotary speed of said reel and varying stepwise, while said cable unit is being wound on said reel in successive layers, the variation in the rotary speed of said member being sufficient to impart to said cable unit a stepwise varying pitch.
 2. A method as set forth in claim 1, wherein said member is rotated in the same direction as saiD reel and at a speed higher than the rotary speed of said reel.
 3. A method as set forth in claim 1, wherein said member is rotated in a direction opposite to the direction of rotation of said reel and at a speed lower than the rotary speed of said reel.
 4. A method of manufacturing a twisted communication cable unit whose twisting pitch varies stepwise from one end of the unit to the other, which method comprises: a. continuously supplying a plurality of elongated strands of laid conductors; b. twisting said strands around each other and thereby forming an elongated cable unit; c. passing said cable unit longitudinally through an apertured member while rotating said member at a constant speed about an axis extending substantially in the direction of elongation of said unit; d. winding said cable unit in sequential layers of increasing diameter on a reel rotating substantially coaxially with said member at a speed proportional to the speed of rotation of said member, whereby said cable unit is passed through said rotary member at a speed varying stepwise as the cable unit is wound on said reel in said sequential layers and the twisting pitch of said cable unit is varied correspondingly.
 5. A method as set forth in claim 4, wherein said member is rotated at a speed higher than the rotary speed of said reel.
 6. A method as set forth in claim 4, wherein said member is rotated at a speed lower than the rotary speed of said reel.
 7. A method of manufacturing a twisted communication cable unit whose twisting pitch varies from one end of said unit to the other end, which method comprises: a. unwinding a plurality of strands of laid conductors from a reel while said reel is being rotated at a constant speed, said strands being initially wound on said reel in a plurality of radially superposed layers; b. passing said strands through an apertured member mounted for rotation substantially coaxial with said reel; c. withdrawing said strands from said member at a speed proportional to the speed of rotation of said reel in a path substantially coinciding with the axes of rotation of said reel and of said member while rotating said reel at a speed different from said constant speed and varying stepwise as said strands are being unwound from said reel, whereby the withdrawn cable unit has a stepwise varying pitch.
 8. A method as set forth in claim 7, wherein said member is rotated in the same direction as said reel and at a speed higher than the speed of said reel.
 9. A method as set forth in claim 7, wherein said member is rotated in a direction opposite to the direction of rotation of said reel and at a speed lower than the speed of said reel.
 10. In a method of manufacturing a twisted communication cable unit whose twisting pitch varies from one end of said unit to the other end, the steps of: a. unwinding a plurality of strands from a reel while rotating said reel at a constant speed, said strands being initially wound on said reel in radially successive layers; b. passing said strands through an apertured member while rotating said member substantially coaxially with said reel at a constant speed proportional to the speed of rotation of said reel; and c. withdrawing said strands from said rotary member at a speed varying stepwise while said strands are being unwound from said successive layers on said reel and thereby twisting said strands at a stepwise varying pitch.
 11. In a method as set forth in claim 10, said member being rotated at a speed higher than the rotary speed of said reel.
 12. In a method as set forth in claim 10, wherein said member is rotated at a speed lower than the speed of said reel.
 13. A method of manufacturing a twisted strand for use in a communication cable, the twisting pitch of said strand varying from one end of said strand to the other end, which method comprises: a. separately supplying a plurality of elongated component conductors at a constant rate; b. twisting said component conductors around each other for forming an elongated strand; c. longitudinally passing said strand through an apertured member mounted for rotation about an axis substantially longitudinal of said strand; d. winding said strand on a reel while rotating said reel substantially coaxially with said member at a constant speed proportional to said rate; and e. rotating said member at a speed different from said constant speed and varying stepwise while said strand is being wound on said reel in successive layers, and thereby varying the twisting pitch of said strand.
 14. A method as set forth in claim 13, wherein said member is rotated in the same direction as said reel and at a higher speed.
 15. A method as set forth in claim 13, wherein said member is rotated in a direction opposite to the direction of rotation of said reel and at a speed lower than the rotary speed of said reel.
 16. A method of manufacturing a twisted strand for a communication cable, the twisting pitch of said strand varying stepwise from one end of said strand to the other end, which method comprises: a. separately supplying a plurality of elongated component conductors; b. twisting said conductors around each other to form an elongated strand; c. longitudinally passing said strand through an apertured member while rotating said member at a constant speed about an axis longitudinal of said strand; d. winding said strand on a reel in radially successive layers while rotating said reel substantially coaxially with said member and at a constant speed proportional to the rotary speed of said member, whereby said strand is moved through said member at a rate which varies stepwise at the completion of each of said layers, thereby imparting to said strand a correspondingly varying twisting pitch.
 17. A method as set forth in claim 16, wherein said member is rotated at a speed higher than the rotary speed of said reel.
 18. A method as set forth in claim 16, wherein said member is rotated at a speed lower than the rotary speed of said reel.
 19. A method of manufacturing a twisted strand for use in a communication cable, the twisting pitch of said strand varying from one end of the strand to the other, which method comprises: a. unwinding a plurality of parallel component conductors from a reel while rotating said reel at a constant speed; b. passing said conductors through an apertured member mounted for rotation substantially coaxial with said reel; and c. withdrawing said conductors from said member at a constant rate proportional to the speed of rotation of said reel in a path substantially coinciding with the axes of rotation of said reel and of said member; and d. rotating said member at a speed different from the rotary speed of said reel and varying stepwise while said conductors are being unwound from said reel for thereby twisting said conductors into a strand of varying pitch.
 20. A method as set forth in claim 19, wherein said member is being rotated in the same direction as said reel and at a higher speed.
 21. A method as set forth in claim 19, wherein said member is being rotated in a direction opposite to the direction of rotation of said reel and at a lower rotary speed.
 22. A method of manufacturing a twisted strand for use in a communication cable, the twisting pitch of said strand varying from one end of the strand to the other, which method comprises: a. unwinding a plurality of parallel component conductors from a reel while rotating said reel at a constant speed, said conductors initially being wound on said reel in a plurality of superposed layers; b. passing said conductors through an apertured member while rotating said member substantially coaxially with said reel at a speed proportional to the speed of rotation of said reel; and c. withdrawing said conductors from said member in a path substantially coinciding with the axes of rotation of said reel and of said member at a rate vaRying stepwise and thereby twisting said conductors into a strand.
 23. A method as set forth in claim 22, wherein said member is rotated at a higher speed than said reel.
 24. A method as set forth in claim 22, wherein said member is rotated at a lower speed than said reel.
 25. A method of manufacturing a communication cable unit which comprises: a. supplying a plurality of strands of laid conductors at a constant first rate; b. twisting said strands around each other and thereby forming an elongated cable unit; c. longitudinally passing said unit through an apertured member mounted for rotation about an axis substantially coinciding with the elongation of said unit; d. winding said unit on a reel while rotating said reel in a first direction substantially coaxially with said member at a constant first speed proportional to said rate while rotating said member at a speed different from the speed of rotation of said reel and varying stepwise as the cable unit is being wound on said reel in successive layers, whereby said cable unit is twisted at a pitch varying stepwise; e. unwinding said cable unit from said reel while rotating said reel in a second direction opposite to said first direction and at a constant second speed different from said first speed; f. passing the unwound cable unit through said member; and g. withdrawing said cable unit from said member at a second rate different from said first rate while rotating said member at a speed different from said second speed and varying stepwise as said cable unit is being unwound from said reel for thereby changing said varying pitch.
 26. A method of manufacturing a communication cable unit which comprises: a. supplying a plurality of strands of laid conductors at a constant rate; b. twisting said strands around each other and thereby forming an elongated cable unit; c. longitudinally passing said unit through a apertured member mounted for rotation about an axis substantially coinciding with the elongation of said unit; d. winding said unit on a reel while rotating said reel in a first direction substantially coaxially with said member at a constant first speed proportional to said rate while rotating said member at a speed different from the rotary speed of said reel and varying stepwise as the cable unit is being wound on said reel in successive layers, whereby said cable unit is twisted at varying pitch; e. unwinding said unit from said reel while rotating said reel in a second direction opposite to said first direction at a second constant speed different from said first constant speed; f. passing the unwound unit through said member while rotating said member at a constant speed proportional to said second constant speed; and g. withdrawing said cable unit from said member at a speed varying stepwise while the unit is being unwound from said reel and thereby changing the twisting pitch of said withdrawn unit.
 27. A method of manufacturing a communication cable unit which comprises: a. supplying a plurality of strands of laid conductors; b. twisting said strands around each other and thereby forming an elongated cable unit; c. longitudinally passing said cable unit through an apertured member while rotating said member at a constant speed about an axis substantially coinciding with the elongation of said unit; d. winding said unit on a reel in successive layers while rotating said reel in a first direction substantially coaxially with said member at a first constant speed proportional to the rotary speed of said member, whereby said cable unit is passed through said member at a speed varying stepwise as each layer on said reel is completed, and the twisting pitch of said cable unit is varied in corresponding steps; e. unwinding said cable unit from said reel while rotating said reel in a second direction opposite to said first direction at a second constant speed different from said first speed; f. passing the unWinding unit through said member; and g. withdrawing said unit from said member at a constant speed proportional to the speed of rotation of said reel while rotating said member at a speed different from the rotary speed of said reel and varying stepwise as said unit is being unwound from the reel for thereby changing the pitch of said unit.
 28. A method of manufacturing a communication cable unit which comprises: a. supplying a plurality of strands of laid conductors; b. twisting said strands around each other and thereby forming an elongated cable unit; c. longitudinally passing said unit through an apertured member while rotating said member at a constant speed about an axis substantially coinciding with the elongation of said unit; d. winding said unit on a reel in radially successive layers while rotating said reel substantially coaxially with said member in a first direction at a constant first speed proportional to the speed of rotation of said member, whereby said unit is moved through said member at a speed varying stepwise as each of said layers is completed, and whereby the twisting pitch of said unit is varied in corresponding steps; e. unwinding said unit from said reel while rotating said reel in a second direction opposite to said first direction at a constant second speed different from said first speed; f. passing said unit through said member while rotating said member at a constant speed proportional to said second constant speed and thereby increasing said pitch of the unit.
 29. A method of manufacturing a strand for use in a communication cable which comprises: a. separately supplying a plurality of component conductors at a constant rate; b. twisting said conductors around each other and thereby forming an elongated strand; c. passing said strand through an apertured member mounted for rotation about an axis substantially coinciding with the elongation of said strand; d. winding said strand on a reel while rotating said reel in a first direction substantially coaxially with said member at a constant first speed proportional to said rate; e. rotating said member at a speed different from the speed of said reel and varying stepwise as said strand is being wound on said reel in radially successive layers, thereby imparting to the strand a twist of stepwise varying pitch; f. unwinding said strand from said reel, while rotating the reel in a second direction opposite to said first direction at a second constant speed different from said first speed; g. passing the unwinding strand through said member; and h. withdrawing said strand from said member at a constant rate proportional to the second speed of rotation of said reel, while rotating said member at a speed different from said second speed and varying stepwise, thereby increasing the pitch of the withdrawn strand.
 30. A method of manufacturing a strand for use in a communication cable which comprises: a. separately supplying a plurality of component conductors at a constant rate; b. twisting said conductors around each other and thereby forming an elongated strand; c. longitudinally passing said strand through a member mounted for rotation about an axis substantially coinciding with the elongation of said strand; d. winding said strand on a reel while rotating said reel substantially coaxially with said member in a first direction at a constant first speed proportional to said rate; e. rotating said member at a speed different from the rotary speed of said reel and varying stepwise as said strand is being wound on said reel in radially successive layers, thereby varying the twisting pitch of said strand in corresponding steps; f. unwinding said strand from said reel while rotating said reel in a second direction opposite to said first direction at a second constant speed different from said first speed; g. passing said strand through said member while rotating said member at a constant Speed proportional to said second speed; and h. withdrawing said strand from said member at a speed varying stepwise as the strand is being unwound from said reel.
 31. A method of producing a strand for use in a communication cable which comprises: a. separately supplying a plurality of component conductors; b. twisting said conductors about each other and thereby forming an elongated strand; c. longitudinally passing said strand through an apertured member while rotating said member at a constant speed about an axis substantially coinciding with the elongation of said strand; d. winding said strand in radially successive layers on a reel while rotating said reel in a first direction substantially coaxially with said member at a first constant speed proportional to the rotary speed of said member, whereby said strand is moved through said member at a speed varying stepwise when each of said layers is completed, and the twisting pitch of said strand is varied stepwise; e. unwinding said strand from said reel while rotating said reel in a second direction opposite to said first direction at a second constant speed different from said first speed; f. passing the unwinding strand through said member; and g. withdrawing said strand from said member at a constant rate proportional to said second speed while said member is being rotated at a speed different from rotary speed of said reel and varying stepwise as said strand is being unwound from said reel for thereby increasing the pitch of said strand.
 32. A method of manufacturing a strand for use in a communication cable which comprises: a. separately supplying a plurality of component conductors; b. twisting said conductors about each other for forming an elongated strand; c. longitudinally passing said strand through an apertured member while rotating said member at a constant speed about an axis substantially coinciding with the elongation of said strand; d. winding said strand on a reel in radially successive layers while rotating said reel in a first direction substantially coaxially with said member at a constant first speed proportional to the speed of said member and thereby moving said strand through said member at a speed varying stepwise as each of said layers is completed and for thereby varying the twisting pitch of said strand; e. unwinding said strand from said reel while rotating said reel in a second direction opposite to said first direction at a second constant speed different from said first speed; f. passing the unwinding strand through said member while rotating said member at a constant speed proportional to said second speed; and g. withdrawing said strand from said member at a speed varying stepwise as the strand is being unwound from said reel and thereby increasing said pitch thereof.
 33. In a method of manufacturing a communication cable unit, the steps of: a. unwinding radially successive layers of two strands of laid conductors from respective reels while rotating said reels at a constant speed about a common axis; b. passing said strands through respective members mounted for rotation substantially coaxially with associated ones of said reels; c. passing at least one of said strands axially and centrally through one of said reels and the associated member; d. withdrawing said strands at a constant rate proportional to said speed and in a path substantially coinciding with said common axis; and e. rotating said members at respective speeds different from the speeds of the associated reels and varying stepwise as said strands are being unwound from said reels as each layer is exhausted, whereby said strands are imparted corresponding varying twisting pitches.
 34. In a method of manufacturing a communication cable unit, the steps of: a. unwinding radially successive layers of two strands of laid conductors from respective reels while rotating said reels at a constant speed about a common axis; b. passing said strands through respective members associated with said reels while rotating said members substantially about said common axis at a constant speed proportional to the rotary speed of said reels; c. passing at least one of said strands axially and centrally through at least one of said reels and the associated member; d. withdrawing said strands in a path substantially coinciding with said common axis at a speed varying stepwise as said strands are being unwound as each layer is exhausted, whereby said strands are imparted twists of correspondingly varying pitches.
 35. In a method of manufacturing a strand for use in a communication cable, the steps of: a. separately unwinding radially superposed layers of component conductors from respective reels while rotating said reels at a constant speed about a common axis; b. passing said conductors through respective members associated with said reels and mounted for rotation substantially about said common axis; c. passing at least one of said conductors axially and centrally through at least one of said reels and the associated member; and d. withdrawing said conductors at a constant rate proportional to said constant speed in a path substantially coinciding with said common axis while rotating said members at respective speeds different from said constant speed and varying stepwise while said conductors are being unwound from said reels for imparting to said conductors twists varying in pitch. 